Audi S3 vs BMW M135i vs Mercedes A45 AMG: Comparison

By Georg Karcher, 06 Sep 2013Power-of-M

Gentlemen, start your engines for a two-day no-holds-barred 2013 shootout between the Audi S3, the BMW M135i and the Mercedes A45 AMG.

It felt like yesterday: same roads, same routes, same silly speed. We used to be driving ourselves dizzy here in trick Mitsubishi Lancer Evos and Subaru Imprezas on steroids, relatively affordable fast cars that loomed large inside our heads and on our bedroom walls.

Ten years on, however, the once untouchable four-door Japanese batmobiles are about as en vogue as the Nokia 3110 mobile phone or a Rio MP3 player. The compact crackerjacks most petrolheads embrace in 2013 still can be had with four doors, four-wheel drive and turbocharged four-cylinder engines, but they are no longer street-legal derivatives of rally-bred icons made in the Far East.

It's Deutschland uber Alles these days, premium eclipsing mainstream, Freude durch Kraft dressed up in more socially acceptable formats. Offering a similar mix of exciting dynamics, engineering excellence and fire-breathing performance, the new masters of the super-GTi segment are the top-of-the-line versions of the Audi A3, the BMW 1series and the Mercedes A-class. In the not too distant future, this group would have starred the 360bhp BMW M2 and the 380bhp Audi RS3, but right here and now the 360bhp MB A45 AMG is facing the 300bhp S3 and the 320bhp M135i. Gentlemen, start your engines for a two-day no-holds-barred shootout on the Dolomites' finest tyre-shredding, brake-eating turf.

Perhaps Mercedes should have known better and offered its silver fox clientele a less uncompromising A-class. One that looked friendlier, had a taller roofline and more rear headroom, not to mention a bigger boot and a softer suspension. Trouble is, this model already exists. It's called B-class and it aims, by and large, at well to do pensioners with near-zero affinity to vehicle dynamics. The target of the third-generation A-class are 30-somethings, dinks and chippies, yuppies and trendy urbanites. This audience is primarily interested in what street cred is made of: style, handling, performance and up-to-date convenience. True, the new A-class should ride better, it could do with adjustable dampers, and the dual-clutch transmission has its foibles. But these flaws can be fixed, and the packaging & visibility issues pale against the Merc's handling and roadholding virtues, its ability to surprise and delight, the sensation of being different from the pack in a way only Audis and BMWs used to be different.

Enter the fully loaded A45 AMG test car, a compact crackerjack costing almost as much as a naked C63 AMG. It is painted matte pewter, runs on black multispoke 19in alloys with polished flanges, and shows off the optional carbon fibre body kit which costs about as much as a six week package holiday in Mallorca. Mercifully Mercedes spared us the AMG aero treatment which makes the aforementioned Evo and Scooby look positively inconspicuous. Pretty? Beauty is in the eye of the beholder who will likely concede that the A45 does have presence, overtaking prestige and the kind of novelty value which makes smartphones work overtime. The pursed snout is however a little long in profile, and the behind may be too broad and squashed for some liking, but the proportions are striking and there is no danger of mistaking the real thing for a tarted up A180.

Still very much on subjective ground, we wonder how the 1series could ever be type-approved for daytime operation on public roads. Even in M sports livery, this is at best a mediocre piece of design which does not get any prettier when you climb into the sombre plastic wonderworld the cabin is best described as. There is no doubt about it: BMW has a problem with perceived quality, which is not helped by the fact that it also affects the 3, 5 and 6series. While the A45 looks and feels more expensive in most places, in this respect even the Mercedes ranks one notch below the Audi which is expertly put together of classy materials. So why is the must-have appeal of the S3 still only a 7 on a scale that stretches to 10? Because the cockpit layout is rather bland, because the three-door model fails to match the visual balance of the five-door Sportback out later this year, and because the S3 looks too much like an A3 S-line with four instead of two exhaust endpipes.

Normally in June, all passes connecting Italy to Austria and Switzerland are open, but since this spring is an autumn which has been pulled forward, evidently erasing summer in the process, we had virtually the entire alps to ourselves. Wherever a sign read Road Closed due to Snow, there was between 20 and 30 kilometres of virtually traffic-free dream territory lying ahead. Add to this a felt 50 miles of visibility, and you are on the threshold of driver's paradise. As luck would have it, not all cars arrived in the required specification, which resulted in the widest possible variety of drivetrain and suspension options. Our S3 was one of the very few specimen not fitted with the desirable S-tronic transmission. The manual shifter works well - short throws, positive action, pragmatically spaced gears, but at 5.2sec, it loses 0.4sec from 0-62mph to the dual-clutch equivalent simply by taking more time to pass on the slices of the nicely stacked torque cake. At 380Nm, the turbocharged 2.0litre unit is not quite as well-endowed as its rivals, and yet it rolls out the dough all the way from 1800 to 5500rpm. Even dedicated clutch devotee will struggle to ignore the virtues of the S-tronic which include intuitive shift paddles, a coasting mode to be summoned in the efficiency programme, a launch control function and the loud automatic blipping of the throttle during gear changes in the dynamic programme. Maturity deficiency syndrome? Be my guest, buy an A3 2.0 TDI instead.

Our M135i came with the optional eight-speed automatic which may be not be particularly M-like but is extremely convenient. It would even be more perfect if there was a positive deterrent between park and drive to secure the lever in reverse, if the transition from sport to manual (to the left of the main gate) was less fiddly, and if coasting was part of the Eco Pro software. While left-hand drive M135i models can be specified with xDrive awd, rhd cars can not, which is odd since the UK car configurator already lists a 120xd. Through the countless hairpins, up steep slopes, and on a very mixed bag of winding roads, the absence of driven front wheels and a limited-slip differential looked at the beginning of our drive like a deciding dynamic deficiency of the BMW - but we were wrong. Thanks to its good dynamic weight distribution, the chip-controlled traction management and those fine composed-to-order Michelin Pilot Supersport tyres, the M car rarely put a foot wrong. Unlike the Z4 engine which fields two parallel turbochargers and that sweet seven-speed DKG, the 3.0litre straight six of the M135i makes do with a single twin-scroll charger and with said ZF automatic. Shaped like a Bavarian beer garden table, the torque curve plateaus from 1300 to 4500rpm at a constant 450Nm.

The discontinued Audi RS3 employed a 2.5litre five to generate 340bhp, thereby matching its closest natural enemy, the 1series M coupe. Only twelve months after their demise, both German kings of the fast lane would have been dethroned by the A45 AMG which squeezes 360bhp out of its turbocharged 2.0litre engine. Although it lacks two cylinders and 1000cc vis-a-vis the BMW, the peak twist action is an identical 450Nm. Again, full muscle is maintained over a wide rpm band, namely from 2250 to 5000rpm. To turn this torque punch into a mighty kick in the butt, the AMG engineers mated their reinforced seven-speed DKG to an aggressively tuned 4Matic driveline. The software of the Speedshift box was borrowed from the SLS AMG GT, which is why the sportiest A-class, too, features three driving modes, a computer-generated heel-and-toe action, a racestart function and in manual/sport the same ultraquick shift times as the flagship gullwing coupe. In C (for controlled efficiency), friends of the earth may relish start-stop and super-smooth gear changes at low revs. In S, the same process is repeated at a brisker pace. In M, you do the shifting, so don't expect the black box to help out when the needle of the rev counter suddenly hits 6250rpm. Good: on-demand M allows you to play the paddle piano for individual driving manoeuvres without first pushing the select button. Bad: the transmission will not accept early downshift orders. In will in fact only shift down when it reckons that the revolutions are evenly matched, which definitely takes too long on the fast approach to a slow bend.

WRX STI and Evo I-X ran turbochargers the size of an infant's head, causing serious throttle lag followed by even more serious forward thrust. In the wake of these two wild winged warriors the motor industry has learned a lot about the art of turbocharging, virtually eliminating delay to throttle orders in the process. At least that's what we thought before setting off on the trails of Hannibal in these highly tuned triplets. No more turbo lag? Hop into the S3, and the ancient vice is back, large as life and annoying. The extra-cost S-tronic may to an extent cushion the effect, but in the manual version one must change down early to keep at least the bottom two LEDs of the boost gauge lit most of the time. Which is a shame because after the delay there is always enough oomph on tap to zoom the car towards the next apex. It takes an adjustment in attitude and timing to step on the gas earlier so that little momentum is lost when snow white is propelling herself onto the next straight. Perhaps this occasionally blurred communication between accelerator and engine control is partly due to the fact that the 2.0TFSI unit redlined at 6500rpm blends direct injection (at low and high load) with indirect injection (at part load). The totally theoretical claimed fuel consumption of the 1415 kilo Audi is 40.8mpg.

Did the SLS-inspired A45 AMG convince us with a rapid-fire throttle response? Yes and No. In combination with the new exhaust (for reduced back pressure) and the advanced fuel injection (for improved thermodynamic efficiency), the twinscroll charger (which runs at a high 1.8bar) swings the whip hard and early. It's the DCT which can undermine this effort by sometimes preselecting the wrong ratio, by taking a little too long to make up its electronic mind now and then, and by occasionally triggering a counter-productive upshift. A software issue perhaps, but one that needs addressing. On a different front, the MB chips do a splendid job relaying a hackle-raising sensation of speed. By momentarily retarding ignition and injection, they make leadfoot upshifts sound almost V8-like, they voice an angry blat-blat during downshifts, and they telegraph a catchy cocktail of charger whine and wastegate whistle into the cabin. Very artificial, but rather nice. With Racestart active, the 1555kilo 360bhp A-class will howl in 4.6 sec from 0-62mph. The official consumption on optional 19in rubber is 39.8mpg. Spend a small fortune on the AMG drivers pack, and the Affalterbach power brokers will kindly raise the top speed from 156 to 169mph which almost equals 6250rpm or the engine's cut-out speed.

If the A45 is Darth Vader on the prowl and if the S3 is Zorro on his day off, then the M135i is Robin en route to lunch with Catwoman. Forget the German hot hatch competition, forget the Japanese Playstation connection, forget the fact that there is an M in this BMW's model designation. Marketing calls these niche models M Performance Automobiles (MPA), and that's exactly what the M135i is: M make-up plus a performance engine and chassis, all wrapped up in the clothes of a compact gran turismo. Believe it or not, but the high-end 1series makes the charismatic M coupe pale in more ways than one. How come? Because the halfbreed M car is benign instead of brutal, cosetting instead of crash-bang hard, relaxed instead of highly strung, easily accessible instead of radically focused. For a start, the 320bhp in-line six runs out of revs at an unambitious 5800rpm, it takes a relatively leisurely 5.1sec to satisfy the stopwatch squad, and its on-paper consumption is a comparatively unexciting 35.3mpg. On the credit side, any trace of turbo lag disappears inside the fantastic ZF box, the mighty mid-range urge puts the four-cylinder competition into perspective, and there are absolutely no artificial ingredients involved in making this 3.0litre motor sound spine-tinglingly good when the mixture gates open.

The BMW also is clearly the most comfortable car in this group. Even with the driving experience selector in sport or sport plus, the suspension will soak up most vagaries with a smile. Like the Audi, the BMW is available with three or five doors, and with manual or let-me-do-this-for-you transmission. Included in the standard M pack are 18in wheels with 225/40 tyres up front and 245/35 footwear in the rear, sports suspension, sports brakes and variable-rate sports steering. The M135i was our number one choice on the poorly maintained Italian autostrade, but it is a touch too laid back to bring your blood to the boil on those memorable alpine special stages. The brakes are furthermore on the soft side when pushed, the quick steering (only two turns from lock to lock) feels overdamped and undertransparant, and there is more roll and pitch and dive than we expected from a 1series model wearing the M badge. Grip on the other hand is astounding in the dry, traction is only an issue when you ask for it by switching off ESP, and the stability through very quick uneven corners is supported by the nicely compliant spring and damper setting. So, full marks for ride quality, panache and refinement, but only 3.5 stars out of five for absolute sportiness and driver involvement.

Especially at a 10/10 pace, the S3 is even easier to drive than the BMW, which in turn feels significantly softer edged than the 1series M. While the M135i will want to understeer into a corner and oversteer at the exit, the Audi goes round bends like a slot racer with a second pin between the rear wheels. Neutrality is the name of its game, modularity ranks only second on its priority list. Boring? Wrong term. The S3 rewards its driver with a different potpourri of talents. The roadholding is for instance so tenacious that we checked the Conti Sportcontact tyres (225/40 R18 all round) for magnetic metal flakes and hidden velcro strap fragments. The steering, overly light and a little mum, nonetheless turns honing the line into a surprisingly entertaining pasttime. The attentive and easy to modulate brakes are strong enough to push the point of no return way past the apex. Thanks to these super-sharp anchors, the reassuring tyre grip and a guardian angel named quattro, the 300bhp S3 can up to a point stay in touch with its 320 and 360bhp challengers. Eventually, the gap will widen and the Audi will drop back, still gracefully maintaining its composure. The car from Ingolstadt is tight-lipped, monosyllabic and reserved, strangely robotic in the way it performs, and flawed in its ability to turn a near-faultless performance into a tangible feelgood experience.

The A45 AMG is not just engine and badges and butch looks. It also boasts a heavily revised front and rear suspension with firmer mountings, recalibrated springs and firmer fixed-rate shock absorbers, fatter anti-roll bars and a reduced ride height. Also new are the variable-effort but constant-rate steering, the high-performance brakes with ventilated and cross-drilled discs all-round, the more lenient stability control, and the latest-generation 4-Matic which diverts up to 50percent of the torque to the rear wheels. The price you pay for all these goodies is about 20percent higher than what Audi and BMW charge you for their best efforts. We say the Mercedes is worth the premium - simply because it is the more exhilarating drive. The engine delivers quantifiable extra urge with real authority, the steering fuses input and feedback to a wonderfully three-dimensional level of control, four-wheel drive distributes torque with the eerie professionalism of a poker ace dealing his rounds, and the brakes bite with vigour and determination until, at the foot of the pass, smoke signals beg for mercy. The A45 AMG is as chuckable as it is sure-footed. It can corner on three wheels, decelerate at a ridiculous yaw angle, put the power down even earlier than the Audi. What it cannot do is ride well, period. Even on smooth blacktop, it is patently obvious that eiderdowns were not on the shopping list.

Would the M135i have won if it looked better and felt more special inside? It might have come closer, but it would still be more of a GT than a GTS. Would the S3 have won if Audi managed to remove multiple layers of indifference and artificiality from what is, in essence, a solid concept? We would love to see the Quattro division succeed in making good cars great again, but the S3 (and the RS6) are tuned primarily for perfection, which is seldom synonymous with excitement. So after 48 hours, 645 kilometres, 269 litres of four-star and three fresh shirts, the A45 AMG takes the trophy ahead of the BMW and the Audi, off-putting price tag and compromised packageing notwithstanding. The M135i feels like a neatly spiced up 1series, the S3 feels like an S-line A3 with more poke. In contrast, the A45 feels more AMG than A-class, more special than mainstream, more bespoke than bespoilered. For the time being, this Mercedes rules the microcosm that was once owned by Scooby, Mitsu & friends. But as soon as the M2 and the next RS3 are ready to pick up the gauntlet, we shall return to the big skies and to the dream driving roads for an encore.

BMW Four stars Love: Engine, transmission, ride Hate: Design inside and out, not really an M car Verdict: Wait for the facelift out next year